This feels like something you can usually only get away with if you’re the mythical 10x rockstar developer. The employer has lots of options. You are merely one

This feels like something you can usually only get away with if you’re the mythical 10x rockstar developer. The employer has lots of options. You are merely one of them. They already rule out tons of applicants on arbitrary criteria. The power imbalance is why wasting the applicant’s time is perfectly fine, but if you want the interviewing party to show you proprietary code or give you employee contacts, that means you’re making additional work for them, and you’re not 100% on board with this place yet, so why are they wasting time on someone who seems skeptical (maybe not a “team player”) and might not even accept their offer?